Radio antenna



W. M. VENABLE RADlO ANTENNA Dec. 1, 1936.

Filed March 5, 1955 'WAQXMM Patented Dec. 1, 1936 UNITED STATES RADIO ANTENNA Application March 5, 1935, serial No. 9,390

10 Claims.

This invention relates to radio antennae, and more particularly to an antenna of the vertical tower type for radiating or broadcasting purposes. l

It is known to those skilled in the art that a number of parallel wires symmetrically disposed about a common axis are, for the purpose of broadcasting, more effective with a less expenditure of power than a single wire, whether such symmetrical arrangement of wires is disposed substantially horizontally or is arranged in a vertical position. It is also known that for broadcasting parallelto the earths surface, i. e., for general broadcasting purposes, in all directions from a given station as a center, vertical antennae are more effective than antennae arranged in any other direction. For this reason, among others, vertical structural towers formed of conducting metal, insulated at their bases, have re-V cently come into quite extensive use. The towers are ordinarily quite slender in comparison with their height, the towers usually tapering toward the top. Sometimes the towers are in the form v of a single structural mast having a single insulating support at the base and maintained in vertical position by means of guy wires. Other towers have a plurality of legs which are-supported on specially constructed insulators. These towers taper from a point adjacent the base toward the top. The taper toward the top of the mast or tower in either case is advantageous from a structural point of view, because it offers less surface to the wind and is consequently less expensive than a tower of uniform section throughout its height capable of withstanding high wind velocities. However, a tapering tower is less eicient for broadcasting purposes than if the top portion of the tower were wider and broader.

An example of a tower for this purpose having a single supporting base is found in Patent No. 1,897,373 to Gerten et al., dated February 14, 1933, while an example of a type of mast having a plurality of legs carried on insulating supports is ldisclosed in the patent to Jenner No. 1,937,968, dated December 5, 1933. The present invention is applicable to either of these types of towers. For the purpose of illustration only, the invention has been specifically described and shown in connection with a tower supported without guy Wires.

The patents referred to show the towers as being comprised of conducting material. They are connected directly into and form the antenna ifforf'the broadcasting circuits. According to the present invention the e'iciency of antennae gofl thisjvtype is improved andlthe effect. on broad.

casting, efficiency due' to the ltaper of the towerrpflENfr OFFICE in the-upper seotions'isv overcome without, how-y ever, adding materially tothe cost of the tower` and withoutv materially increasing the Wind re,

sistance of the tower. In carryingA out the presentinvention, a supporting element is secured to or above the conducting top ofthe metal tower.

From this support` depends a series of vertical wires, all of vvhichare electrically insulatedat their upper ends' from the tower itself and which i are secured attheir lower ends to the conducting tower. These wires, which are preferably symmetricallyk arranged about the vertical axis ofthe. tower, form in effect, a conducting cage of substantially, uniform diameter throughoutits entire height. By reason of this arrangement, the wires surroundingthe tower, because of` their vdis,-` tribution and well-known principles of electro-r magnetic induction, carry most of theenergy effective in broadcasting, the tower itself above the point of attachment ofthe wires carrying but little of the current. Because of this, the effectiveness ofthe antenna as a whole is improved.

'This effectiveness may be `further increased by increasing vtheV electrical 4capacity at the toprv of thewires or wire cage, keeping the capacity of the top of the Atower itself as small as possible.` p

The invention may be vreadily,understood by reference to `the accompanying drawing,.in whichV Figure 2 is a plan View looking down. from the` top. e

Referring to the drawing, the tower itself whichl Figure lis `a vertical view of one form ofy is'designated 2 yand which is usually formed of steel, may be of any known or preferred type of structuralmast.y The tower is showny as VVbeing supportedpn legs carried oninsulators' 4 of a type 'known to those skilled in the art and by means of which the structural tower is insulatedv from the ground while the tower itself is maintained and supported'in vertical position. .The

tower decreases in width from itsbase toward its uppermost point 5. At the top of the'tower is' a pole `or mast 6 which in the construction *shown in'Figure'l may be'of wood, and which carries a spideror frame 1 at the top thereof, this frame having a number of horizontal'arms suitably braced and of equal length. Secured to the outerv end of each o f these arms 8 is a depending wire 9',

the wires-9 preferably extending down to a'poi'nt:l

l0 near the base of the tower where they are electrically connected to the tower. Where desired, the wires may also be supported by the tower and/or attached thereto at the intermediate point marked I l. The upper ends of the wires 9 are, of course, insulated from the top of the conducting tower by reason of the wooden or other insulating pole (i. Preferably, the pole projects an appreciable distance above the top of the conducting tower. Y y

In the drawing, I have shown eight of these Vertical wires 9 symmetrically arranged about the vertical axis of the tower, but this number may be varied as may be desired. Where the supporting frame 8 or spider 'l does not have sufcent inherent capacity, a number of balls I2 may be provided above the spider, one being preferably located at the upper end of each of the wires 9 and by reason of which the capacity of the upper portion of the structure is effectively increased.

By reason of this arrangement it will be seen that the wires 9, in effect, form a of uniform diameter throughout the greater portion of the height of the tower, particularly the upper part thereof. This acts to compensate, so far as radiating efficiency is concerned, for the diminishing width of the conducting tower toward the top. Moreover, by reason of the fact that the upper ends of the wires are insulated from the top of the tower, most of the energy is dissipated from the wires 9 and relatively little from the upper conducting portion of the tower. By increasing the electrical capacity at the top of the wires or of the cage formed by the wires, and by keeping the capacity of the top of the tower itself as small as possible, the effectiveness of the tower is further increased. The effectiveness of the antenna is further increased in the preferred embodiment by reason of the fact that the top of the cage formed by the vertical wires 9 is well above the conducting top of the tower.

In the case of very tall towers, it may be necessary to use a metal pole in place of the wooden pole 6, in which case the metal pole may be insulated from the top of the tower and in which case the wires 9 would be insulated from the supporting pole, the arrangement in such case being designed to provide a minimum capacity coupling between the wires and this upper tower structure.

It maybe noted that the construction illustrated oifers .protection to the wooden pole 6 against lightning, by the presence of the balls I2 at a higher elevation, or at least as high an elevation as the top of the pole. If the spider be of metal and have suflcient capacity so that the balls I2 are not necessary, it is, of course, apparent that the spider may be provided with points to give added protection against lightning discharges.

The advantages of the present invention arise from the fact that the vinres or cage 9 make use of the known principle that a number of parallel wires symmetrically disposed about a common axis are more eifective for broadcasting purposes than a single conductor. vantage resides in the increased `eiliciency resulting from the fact that the upper end of the wires are not connected to the conducting. top

. of the tower, and from the fact that the capacity of the tower is relatively less inside this portion ofthe cage where the upper ends of the wires have no connection to the tower. Further advantages derived from the increased efficiency cylindical cage A further adresult from extending the cage above the conducting top of the tower.

While I have specifically illustrated and described a preferred embodiment of my invention, it will be understood that various changes and modifications may be made therein and that the invention can be adapted to various types of structural masts, all of which changes and modiiications are within the scope of the following claims.

I claim: Y

1. A vertical antenna structure for broadcasting comprising a central supporting tower, a plurality of antenna wires surrounding said tower, said wires being electrically connected to the tower at the lower extremities, the upper extremities of the wires being supported from the top of the tower but insulated therefrom.

2. A vertical antenna structure for broadcasting comprising a central tower of relatively slender shape converging toward its top, a plurality of antenna wires arranged about said tower, said wires having their lower ends electrically con-- of said wires' nected to the tower, the upper ends being supported from the tower but lated therefrom and extending well conducting top of the tower.

being insuabove the 3. A vertical antenna structure for broadcast-- ing comprising a structural mast having a plurality of antenna wires arranged thereabout in trical contact with the mast, said wires being;

electrically connected to the mast at a point well below the top thereof.

4. A vertical antenna structure for broadcasting comprising a conducting structural tower converging toward its top, a plurality of antenna wires surrounding but spaced from said tower substantially parallel with the vertical axis thereof, and means at the top of the tower for supporting said wires out of conducting relation with the top of the tower, said wires being connected to the tower at a point well below the top thereof.

5. A vertical antenna structure for broadcasting comprising a structural tower of conducting material tapering toward the upper end thereof, and a series of wires parallel to the vertical axis of the tower arranged about the outside of the tower in spaced relation thereto, the lowermost ends of the wires being connected to the tower, the upper ends of the wires being insulated from the conducting tower and extending above the conducting top of the tower.

6. A-radio antenna structure for broadcasting comprising a rigid structuralconducting tower having a tapered upper portion and a cylindrical cage comprising vertically extending wires from the tower and its lower portion electrically connected to the tower.

7. A radio antenna structure for broadcasting comprising a series of vertical conducting wires symmetrically arranged to form a cage about a vertical axis, a tower on the same axis within the cage, supporting means at the top of the tower from which the cage is suspended, said supporting means being constructed to insulate the top of the cage from .the tower, the lower portion of each wire comprising the cage and the tower being electrically connected.

8. A radio antenna structure for broadcasting comprising a symmetrical series of parallel wires arranged about a vertical axis, a conducting tower inside the series of wires and substantially co-axial therewith, means at the top` of the tower for supporting said wires at their upper ends with said upper ends insulated from the tower, the lower portions of the wires being electrically connected to the tower, and means at the upper end of the series of wires providing an effective increase of electrical capacity therefor.

9. A radio antenna structure for broadcasting comprising a symmetrical series of parallel wires arranged about a Vertical axis, a conducting tower inside the series of wires and substantially co-axial therewith, means at the top of the tower for supporting said wires at their upper ends with said upper ends insulated from the tower, the lower portions of the wires being electrically connected to the tower, and means at the upper ends of the series of wires providing an effective increase of electrical capacity therefor, said means comprising metal balls at the uppermost ends of the wires.

10. A radio antenna structure for broadcasting comprising a symmetrical series of parallel wires arranged about a vertical axis, a conducting tower inside the series of wires and substantially co-axial therewith, means at the'top of the tower for supporting said wires at their upper ends with said upper ends insulated from the tower, the lower portions of the wires being electrically connected to the tower, and means at the upper ends of the series of wires providing an effective increase of electrical capacity therefor, said means comprising metal balls at the uppermost ends of the wires, the balls constituting the highest part of the antenna structure.

WILLIAM MAYO VENABLE. 

